女,16岁,低热盗汗,腰痛2个月,右髂窝出现肿块,B超检查为液性,右髋关节屈曲活动受限,诊断考虑为
A.颈椎结核B.胸椎结核C.腰椎结核D.髋关节结核
参考答案:C
The computer looks old, but it _________ just half a year ago.
A.has been bought
B.will be bought
C.is bought
D.was bought
具有正常听力的人能够感觉到的频率范围大约为16~20000Hz,人到25岁左右时,对15000Hz以上频率的灵敏度显著降低,当频率高于15000Hz时,听力开始向下移动,而且随着年龄的增长,频率感受的上限逐年连续降低。但是,对于频率小于()的声音,听觉灵敏度几乎不受年龄的影响。
A.500Hz
B.1000Hz
C.2000Hz
D.5000HZ